Generally, this invention relates to the transmission of a signal in association with all or part of a tool string used in drilling oil, gas, and geothermal wells and for all or part of a tool string used in a production well. More particularly, this invention relates to a connection apparatus comprising fixed and rotating inductive transducers that are in communication with each other, a network of downhole inductive transducers along the tool string, and with ground-level equipment, including the World Wide Web.
For more than 50 years proposals have been made for transmitting an electronic signal along the length of the tool string used in the exploration and production of useful hydrocarbons and subterranean energy sources, namely oil, gas, and geothermal energy sources. These proposals have not met with commercial success for reasons associated with the numerous technological obstacles that must be hurdled in order to achieve efficient and reliable connections across the hundreds of tool string components that are required to successfully reach and acquire the underground energy resources. For example, a tool string for an oil well is likely to require hundreds of approximately 30-foot drill pipe segments interconnected at tool joints. In addition to the drill pipe, a series of heavy-weight drill pipe and drill collars may be required to give stability to the string. Moreover, such tools as swivels, reamers, jars, pumps, motors, perferators, turbines, mud-pulse sirens, directional drilling subs, and drill bits are also required in the makeup of a modern-day tool drill string. Each of these tools requires special adaptation for signal transmission in the harsh subterranean environment, which is characterized by high temperatures, vibrations, rotational accelerations, invasive and abrasive fluids, and dynamic stresses associated with suspending a million pounds of drill string components from the surface drill rig.
In a production well similar obstacles are present. A production well may also comprise hundreds of lengths of the interconnected casing and production pipe segments as well as pumps and motors for delivering oil, gas, or geothermal energy resources to the surface. Additionally, high temperatures, fluids and corrosive gases mixed with abrasive particles combine to make the production environment an equally harsh environment for electronic components.
In response to these obstacles, the applicants have invented a network system for signal transmission downhole. The linking element in this system is an inductive transducer which does not rely on rotational orientation and direct contact in order to transmit a signal from one jointed component to another. The inductive transducer is the subject of U.S. Pat. No. 6,392,317, and PCT Application No. 75114A1, both incorporated herein by this reference. The inductive transducer comprises inductive rings that when brought into close proximity with each other, and energized, are capable of producing a shared magnetic field suitable for transmitting the signal from one component to the other. The rings comprise a conductive, insulated wire loop housed within an insulating and magnetically conductive ferrite trough, or groove. In practice, the transducers are coupled as closely together as possible, so that the transducer can be modeled as a transmission line transformer having both capacitive and inductive properties. As a convenience for manufacturing and assembly, the ferrite trough may consist of closely spaced apart ferrite segments. The inductive transducers are normally located at each end of the downhole tool and connected by a coaxial cable or some other conductor means. Additionally, the transducers may be connected to data-gathering sensors and transmitting links at predetermined locations along the tool string in aid of exploration and production of subterranean resources. Such links also serve as signal enhancement stations for error correction and boosting as the signal journeys along the downhole network.
Since a fixed and rotational connection is required to transmit the data to and from the operating tool string, the top-hole swivel has been selected for adaptation by the applicants for signal transmission to and from the downhole network. The top-hole swivel is a key surface-mounted drill rig component in the tool string. It functions as the entry point for drilling fluids and as a load transfer point between the drill string and rig. In some cases it has been used as a data gathering point for logging the well and for monitoring drill string dynamics. When adapted for signal transmission, the swivel becomes the interface between the outside world and the downhole signal transmission network of inductive transducers. Hence, this application presents a top-hole swivel fitted with inductive transducers that are adapted for signal transmission to and from the downhole network.